This project involves studies of the actions of organophosphates on target avian cells and tissues. It focuses on acetylcholinesterases and cholinesterases, cultured muscle and nerve, the mechanisms of toxicity of organophosphates and recovery of cells from their effects. This year a study of chicken cells and tissues supported that the distribution of ACHE forms is regulated during development, that the 20S form of ACHE is localized at the motor endplate, and that ACHE is first synthesized as a low molecular weight form following inhibition with organophosphates. Evidence was obtained that the avian sperm motility may be regulated in part by a system similar to the cholinergic neurotransmitter system, and that the system is affected by organophosphates. Studies of muscle and nerve cells with ouabain, an inhibitor of the Na ion pump, supported that changes in ions regulate AChE and AChR and that this may be one of the ways nerves regulate muscles. A related study of delayed neurotoxicity was inaugurated with an analytical chemist, Dr. J.N. Seiber, and a toxicologist, Dr.J. Knaak, using a mutant featherless chicken. Laboratory and field studies are underway to examine the feasibility of using a special experimental animal as a "sentinal" for organophosphate toxicity in the field.